HARARE, Zimbabwe (AP) -- A Zimbabwean peace activist held in an alleged plot to overthrow President Robert Mugabe has gone missing again, a leading human rights lawyer said Thursday.

Human Rights Watch called for the immediate release of Jestina Mukoko saying the charges she faces "seem politically motivated." The plot Mukoko is accused has been widely dismissed as fabricated, and possibly an attempt by Mugabe's regime to find an excuse to declare a state of emergency.

Zimbabwean lawyer Beatrice Mtetwa said police had refused to comply with a judicial order late Wednesday that Mukoko be taken to hospital so allegations of torture could be investigated. Mukoko had been missing for three weeks before she appeared in court Wednesday and police claimed they were not holding her.

Mtetwa said Mukoko had been moved from the Harare police station where lawyers had managed to track her down, and police would not say where and other activists were being held.

"We now don't even know where they are," Mtetwa said. But "if they disappear, everyone knows that they (police) have them."

The judge who ordered Mukoko and other activists sent to a hospital under police guard Wednesday also called for them to be brought to court Monday to determine the next step. Mtetwa said there was no way of saying whether police would produce anyone.

Mugabe has faced growing pressure to step down. Charging Mukoko, the respected head of a group known as the Zimbabwe Peace Project, is a sign he is not prepared to yield after nearly three decades in power.

The Herald, the state-run daily, said Wednesday that Mukoko and nine members of the main opposition Movement for Democratic Change were accused of attempting to recruit fighters to overthrow Mugabe. The Herald quoted police as saying the MDC was training fighters in Botswana.

Zimbabwean officials have repeatedly made such accusations, which have been denied by Botswana and the MDC. Last week, South African President Kgalema Motlanthe dismissed the allegations, saying the main regional bloc opened an investigation when Mugabe's regime first raised them last month, but "we never believed" them.

A power-sharing deal, signed in September, calls for Mugabe to remain president and MDC leader Morgan Tsvangirai to take the new post of prime minister. One of the unity government's tasks would be preparing for new elections. The agreement has stalled over a dispute about who would control key Cabinet posts - and over charges Mugabe has stepped up harassment of dissidents.

Mugabe, 84, has ruled the country since its 1980 independence from Britain and refused to leave office following disputed elections in March.

Food, medicine, fuel and cash are scarce in Zimbabwe, and critics blame Mugabe's policies for the ruin of what had been the region's breadbasket. Mugabe blames Western sanctions, though the European Union and U.S. sanctions are targeted only at Mugabe and dozens of his clique with frozen bank accounts and travel bans.

Mugabe has faced renewed criticism because his country's economic collapse has led to a humanitarian crisis. Millions of Zimbabweans are in need of food aid and a cholera epidemic has killed more than 1,100 people.